Meteorologists may have found a way to predict some killer heatwaves up to three weeks in advance. Now, the best they can do is about 10 days.
An earlier warning would help cities prepare cooling centres and check on the elderly, said Gerald Meehl, co-author of a study that describes the method. "It gives you a little bit of a heads up of what's coming," he said.
The key may be a certain pattern of high- and low-pressure spots across the globe high in the sky. When that pattern shows up, the chances double for a prolonged and intense heatwave in the eastern two-thirds of the United States, according to the study published on Sunday in the journal Nature Geoscience.
This could predict some types of heatwaves but not all, meteorologists said. The study's authors said they think the pattern occurred before last year's heatwave in much of the central United States, but they still need more work to confirm it.
The researchers at the National Centre for Atmospheric Research in Boulder, Colorado, looked at US heat waves that lasted at least a week and were 3 degrees to 5 degrees Celsius warmer than normal.
They found when high-pressure and low-pressure systems line up in a specific pattern, it foreshadows heat to come in about 15 to 20 days.